Problem: Virtual text indicating runnable code examples in help files is
intrusive and non-configurable (and often denotes actually non-working
examples).
Solution: Remove virtual text.
Problem: It's difficult to navigate large structured text files (vim
help, checkhealth, Markdown).
Solution: Support `gO` for table of contents and `]]`/`[[` for moving
between headings for all these filetypes using treesitter queries.
Refactor: colorization of highlight groups is moved to the `help` ftplugin
while headings-related functionality is implemented in a private
`vim.treesitter` module for possible future use for other filetypes.
Problem:
`yx` uses "y" prefix, which shadows a builtin operator.
Solution:
Use `g=` (in the form of `g==` currently), drawing from precedent of
CTRL-= and 'tpope/vim-scriptease'.
Problem:
Headings in :help do not stand out visually.
Solution:
Define a non-standard `@markup.heading.1.delimiter` group and
special-case it in `highlight_group.c`.
FUTURE:
This is a cheap workaround until we have #25718 which will enable:
- fully driven by `vimdoc/highlights.scm` instead of using highlight
tricks (`guibg=bg guifg=bg guisp=fg`)
- better support of "cterm" ('notermguicolors')
It seems that nvim-treesitter stops treesitter highlight when changing
filetype, so it makes sense for builtin ftplugins to do this as well.
Use :call and v:lua here to allow separation with '|'.
Problem: Not all default highlight groups show their actual colors.
Solution: Refactor `vimhelp.lua` and apply it to all relevant lists (UI
groups, syntax groups, treesitter groups, LSP groups, diagnostic groups).
- Add runtime/lua/vim/vimhelp.lua, which is a translation of Vim's
runtime/import/dist/vimhelp.vim.
- Unlike Vim, run the highlighting from an ftplugin file instead of a
syntax file, so that it is run even if using treesitter.
